Conventionally, a drainage device comprises a drainage valve presenting operation that is modifiable as a function of a measured pressure difference, as described in DE 196 54 990. The pressure difference must then be measured between the inlet and the outlet of a very narrow passage of small diameter, thereby specifically running a major risk of the passage becoming obstructed. Furthermore, a pressure difference sensor generally presents problems of stability and of drift over time.
Also, international application WO 2006/115724 discloses an implantable mass flowmeter suitable for transmitting a signal to the outside of a patient, which signal is representative of a cerebro-spinal fluid flow rate. The flow rate measurement can thus be communicated to a third party. Nevertheless, that flowmeter is not used in association with a device that enables the opening conditions of a drainage valve to be modified.
A particular object of the present invention is to provide an implantable drainage device that does not present the above-mentioned drawbacks.